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In this lesson, we explore Docker’s image registry. Throughout our work, we’ve run many containers using images—but where do these images reside, and how do you access them? All images are stored in a central repository called an image registry. By default, Docker uses Docker Hub, a public registry hosting thousands of both public and private images. You can push your own images to Docker Hub and choose to keep them private.

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Default Registries

On top of Docker Hub, organizations can deploy private registries internally or use managed services from cloud providers:
The image shows a sign-up page for Docker Hub, highlighting its use for building and shipping applications, alongside options for Docker Trusted Registry, Google Container Registry, Amazon Container Registry, and Azure Container Registry.

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Image Categories on Docker Hub

On Docker Hub, images are organized into three categories:
The image shows a registry of software images categorized into "Official Images," "Verified Images," and "User Images," with details like downloads and stars for each entry.

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Searching for Images on Docker Hub

You can browse and search images via the web interface. For example, searching for “Ubuntu” displays official Ubuntu images along with download counts and star ratings:
The image shows a Docker registry interface with a search for "Ubuntu," displaying results for the Ubuntu container image, including details like downloads and stars.

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Working with Image Tags

Each image can have multiple tags. When you pull or run an image without specifying a tag, Docker uses the default tag: latest. This tag points to the version designated by the image maintainers.
Pulling ubuntu is equivalent to pulling ubuntu:latest, which currently refers to Ubuntu 20.04.
To pull a specific version, specify its tag. For example, Ubuntu 18.04 is tagged as bionic, and Ubuntu 14.04 as trusty:

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Listing and Searching Images from the CLI

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List Local Images

To display all images on your host:
Example output:

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Search Docker Hub from Terminal

By default, this returns up to 25 results. To limit the output (maximum 100):

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Filter Search Results

Use filters like stars and is-official to refine results:

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Pulling Images Without Running Containers

If you only want to download an image without starting a container:
Example output:
Verify the image is present:
That concludes this lesson on Docker image registries. In the next lesson, we’ll dive into container management.

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References

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